1. Field of the Invention
An encapsulated liquid level sensor device and a method of encapsulating the liquid level sensor device.
2. Description of the Prior Art
Sensors to monitor liquid levels are well known in the art. Such sensors often include a float member which rises and falls with the changing liquid level in a drain pipe, drain pan or tank. Float actuated switches are commonly used in equipment and systems to prevent overflow of liquid such as condensate in air conditioning and refrigeration systems.
Often such float sensors and switches have been replaced by more reliable electronic probe switch devices. These devices eliminate moving parts generally using instead, a pair of probe sensors for detecting rising water levels.
Further efforts have been undertaken to produce module structures to encapsulate electronic components on circuit boards to protect the components from the surrounding environment are represented by the patent documents discussed below.
U.S. 2002/0189346 relates to a device for sensing a level of a fluid including a microcontroller disposed within a housing and a probe coupled to the microcontroller. The microcontroller applies a given DC potential to the probe for a first period of time, measures a voltage associated with the level of the fluid to be sensed after the first period of time and applies a reference DC potential to the probe for a second period of time.
U.S. 2003/0173707 shows the use of polyamide based molding compositions for the production of moldings and for adhesive sealing or filling in the production of electrical or electronic devices, in particular of plugs, cables, switches, sensors, transponders and modules.
U.S. 2006/0003137 discloses a method of encapsulating a component assembly comprising a first layer having a first set of physical properties and a second layer having a second set of physical properties to protectively surround the component assembly. A continuous transitory material is formed between the first layer and the second layer at associated first and second margin portions such that the first layer and the second layer are not prone to delamination.
U.S. 2006/0171127 describes a control unit including a plurality of electronic parts sealed with a resin.
U.S. 2006/0208915 discloses a liquid level control switch comprising a plurality of electronic components enclosed in a case including electrically conductive sensor-probe pins extend from a PC board and are positioned for detecting liquids at various levels within drains, drain pans, tanks, reservoirs and pipes of various dimensions.
U.S. 2008/0179962 relates to a leak detector pad comprising a circuit board having a bottom surface and a top surface, spaced first and second electrically conductive traces located on the bottom surface, and an electronic circuit mounted on the top surface.
U.S. 2009/0140866 shows a sensor for detecting the presence of a liquid comprising a housing having a concave upper surface, a concave lower surface, and a peripheral wall connecting the upper surface and the lower surface. A plurality of apertures are formed in the wall. A plurality of electrically conductive members extend above the upper surface and below the lower surface and are separated from one another by a gap in which a liquid can accumulate. The electrically conductive members are configured to generate an output signal when a conductive liquid comes into contact with the electrically conductive members and bridges the gap. An output connector is coupled to the plurality of electrically conductive members and is configured to carry the output signal.
U.S. 2009/0268414 teaches an over-molded electronic module includes a frame, an electronic assembly and a polymeric body. The frame includes a sidewall that defines an opening to provide a position for the electronic assembly. The polymeric body is formed of a polymeric composition encapsulating both sides of the electronic assembly and a portion of the frame.
U.S. 2009/0291288 relates to a molded part for bonding to metal or plastic substrates for use as a fastening element comprising a hot melt adhesive based on polyamide, polyolefins, polyesters, polyacrylates or polystyrene.
U.S. 2009/0295027 discloses electrical components mounted on a circuit board sealed within a frame tray of a curable material that encapsulates the circuit board. The electrical components of the circuit board are positioned and sealed within the frame tray such that the cured material does not affect an airflow path which dissipates heat produced by the electrical components during use. The curing of the curable material shields the circuit board from moisture, dust and other environmental contaminates.
U.S. 2010/0050756 shows a drain pan level monitoring system comprising a level sensor to generate a level sensor output signal related to a sensed level of condensation buildup within a drain pan.